Biology 0610 · IGCSE · Asexual reproduction

Asexual reproduction — practice question

Fig. 5.1 illustrates several stages in the reproduction of Escherichia coli. The diagram labels include: loop of DNA; original bacterial cell; bacterial cell increases to a critical length and a copy of DNA is made; daughter cells are formed; daughter cells enlarge.
(a)[3]

Complete the statements about the cells in Fig. 5.1. DNA takes the form of a double ........................................ . DNA is copied so that the number of loops of DNA after cell division is ........................................ in each daughter cell. The daughter cells are genetically ........................................ to the original cell.

(b(i))[2]

Using the information in Fig. 5.2, state the most frequent cell length of the E. coli cells immediately after cell division. Give your answer in millimetres.

(b(ii))[2]

Some students concluded that the cells must be at least $6\,\mu\text{m}$ long before cell division can happen. Describe the evidence that contradicts the students' conclusion. Use the information in Fig. 5.2 to support your answer.

(c(i))[2]

Describe how a plasmid is cut so that a new gene can be inserted into the plasmid.

(c(ii))[2]

State two reasons, apart from the presence of plasmids, why bacteria and single-celled fungi are useful to biotechnology industries.

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